For a semiconductor device such as an LSI, a technique called silicon photonics to establish connection to the semiconductor device through optical waveguides is currently under development to solve a signal delay attributed to metal wiring.
The optical waveguide employs silicon which is translucent to light in a near infrared region, and has a pattern width of several hundreds of nanometers. If this fine optical waveguide has roughness in the size of several nanometers at an edge portion of a pattern, such roughness may cause a large loss and block transmission of optical signals.
Further, when an optical resonator is formed by using the optical waveguide, a wavelength of resonating light changes significantly even with slight variation in the width of a gap portion between patterns.
For these reasons, high-accuracy processing techniques are required to manufacture optical waveguides and optical elements suitable for practical use.
To this end, one conceivable method is to form a pattern in an optical element by using an electron beam exposure apparatus.
However, the line with of the optical waveguide is as large as several hundreds of nanometers. Accordingly, if an electron beam spot of the electron beam exposure apparatus is narrowed to secure required accuracy, a large number of times of irradiation are necessary and it takes long time to draw the pattern.
The above noted conventional technologies are described, for example, in Japanese Laid-open Patent Publication Nos. H08-195339 and 2011-49556.